I wouldn't say they changed anything...simply added to the body of knowledge.

There is a difference to adding to the body of knowledge and changing its direction. There are people whose discoveries or theories are so radical that they do cause the world to think anew. Newton was in the next door College to mine. Even though we are big rivals, I have to admit that he was a paradigm shifter, along with Einstein. My college produced William Harvey, who discovered the circulation of the blood, and Francis Crick who proposed the structure of DNA (along with Jim Watson). Those guys also changed the direction of medicine and science.

I have a 400mm f2.8 IS (the first one) and a 300mm f4, plus both vIII extenders. This gets me a wide range of telephoto options, from 300mm to 1280 (equiv. on the 7D)

The 600mm f4 II looks astonishing, but waaaay past my budjet.

I actually like the 300/2.8 II for wildlife, especially deer and other ungulates. During this time of year especially, the males seem pretty docile. With as little as tan pants and a tan/light greenish camo shirt, they seem fearless enough to let me get well within 300mm range...even as close as 100mm range for a head shot. The weight and balance of the 300mm is a lot better, IMO, for your average walk-around wildlife photography than the 600mm (not that the 600mm isn't a great lens for that as well when you have more stationary or dangerous wildlife subjects.)

Are you trying to tell me that your new $6800 lens takes good photos!!? And it's easier to carry than a lens 2X bigger and heavier!!!? Never!

I am sure it's an awsome lens. I wish you lived next door so I could borrow it. I realy like my 300mm f4 for a walk around anytime. My walk around/hiking "kit" is a 5DIII, 7D, 8-15, 24-105, 300 f4, and 1.4X III

I have a 400mm f2.8 IS (the first one) and a 300mm f4, plus both vIII extenders. This gets me a wide range of telephoto options, from 300mm to 1280 (equiv. on the 7D)

The 600mm f4 II looks astonishing, but waaaay past my budjet.

I actually like the 300/2.8 II for wildlife, especially deer and other ungulates. During this time of year especially, the males seem pretty docile. With as little as tan pants and a tan/light greenish camo shirt, they seem fearless enough to let me get well within 300mm range...even as close as 100mm range for a head shot. The weight and balance of the 300mm is a lot better, IMO, for your average walk-around wildlife photography than the 600mm (not that the 600mm isn't a great lens for that as well when you have more stationary or dangerous wildlife subjects.)

Are you trying to tell me that your new $6800 lens takes good photos!!? And it's easier to carry than a lens 2X bigger and heavier!!!? Never!

I am sure it's an awsome lens. I wish you lived next door so I could borrow it. I realy like my 300mm f4 for a walk around anytime. My walk around/hiking "kit" is a 5DIII, 7D, 8-15, 24-105, 300 f4, and 1.4X III

Hah! Well, I don't actually own it. I rented it a couple times, and will probably buy it within a year or two, because I really do love it for wildlife work. I opted to get the 600mm first, though, as I'm currently really into bird photography (with the intent of mastering it/becoming pro with it in some fashion, before moving back to wildlife and nature in general for the rest of my life ), and the 600mm gets me so much more for birds than the 300mm does.

I opted to get the 600mm first, though, as I'm currently really into bird photography...

That's why I got the 600 II. I do often use it with the 1.4xIII. I suppose if there'd been an 800/5.6 II available, I'd have had a more difficult decision, but since the 600 II + 1.4xIII is a longer FL, lighter than the 800L, and delivers better IQ, choosing between them was easy.

I'm planning to get the 300/2.8 II in the foreseeable future, though...

It is a nice review, though very light in comparison to the excellent reviews at TDP.

I did find this strange:

Quote

Who it’s not for: This is definitely not a lens for the weekend warrior to start with. Those considering buying their first long lens would be better off starting with a shorter focal length such as the Canon 300mm f/4 L IS and then “graduating up to the bigger glass.

I would say that anyone thinking of buying a big white should buy the length that best suits their photography at that moment, and in the foreseeable future. It would be extremely costly to start collecting lenses, and if you can afford a 600 then get it, don't get the 300, then the 400, then the 500 unless you are Bill Gates, or possibly a neurosurgeon, or even a neuroanatomist!

Also, isn't there an error in the:

Quote

A bit on Image Stabilization (from Justin’s text)“Optical Image Stabilizer technology makes hand-held photography more practical at slow shutter speeds*” (*Canon USA). IS helps free the camera and photographer from the tripod and gives you a bit more latitude to how and where you shoot. As a guide, it’s suggested that photographers’ shutter speeds should match the apparent focal length of the lens. So ideal shutter speeds on a full frame camera like the 1DX, 5DMKIII, or 6D, would be about 1/300th of a second at 300mm

As this is a review of a 600mm lens, shouldn't it be 1/600th? It looks like someone copy and pasted from a 300 review. But I am often wrong about these things.

I opted to get the 600mm first, though, as I'm currently really into bird photography...

I'm planning to get the 300/2.8 II in the foreseeable future, though...

These are my actual 2 great whites. The 300/2.8 II is the sharpest lens of my whole collection. Light and easy to handle. If you habe both FF and aps-c, this focal lenght is a logical addition. this lens is really excellent ;-)

Of course you gain by going from 400 to 600mm - I have done it. Your arguments jrista are qualitative as to the amount of gain and are hand waving that it goes up by the focal length squared. But, the physics and maths quantitatively show it varies linearly with length. Let us just agree that it is a great improvement.

I went up to 600mm by using a 300mm f/2.8 II +2xTC III. It may not be quite as good as the native, but it is good enough and so light that I can hold it in my elderly hand for hours.

Here is a 100% crop of a heron 50-60 metres away I took on Sunday.

Perhaps an actual visual example from a world renown bird photographer can settle the argument. Art Morris, literally renown as the worlds best bird photographer, also agrees the gain is relative to the square of the difference in focal length, not the linear difference:

Support for an opinion may be comforting but doesn't prove or settle arguments. Art Morris often changes his mind. For many years, he much preferred the 400 f/5.6 (his "toy" lens) over the 100-400mm. Then he decided the zoom was better. For years, he argued against the 300mm f/2.8, then recently he changed his mind and decided it was great for bird photography.

I think all that is beside the point. Just look at the animated image...the bird clearly grows four times larger in area...not two times. It goes from covering about 20% of the frame to 80% of the frame. That is what I was trying to demonstrate. If you halve your angle of view, you halve it in both the horizontal and vertical...which means a 600mm lens covers 1/4 the scene area as a 300mm lens....if you shoot the same scene from the same physical spot with a 300mm lens and a 600mm lens, you could produce the same angular result with the 600 if you photographed the upper left, upper right, lower left, and lower right areas, and stitched them together.

That isn't a matter of opinion or personal preference...it's a matter of physics and math. Art Morris can't change his mind about that.

If you double the linear dimension, you quadruple the area. That is simple arithmetic. But, as any mathematician or scientist knows: the resolution of a lens depends simply on the linear dimension - you get twice, not quadruple the resolution on doubling the focal length; and the increase in precision or S/N depends on the square root of the area (number of pixels of the same sensor used) - you get twice the S/N, not quadruple. I can double the length and quadruple the area of a photo in Photoshop or with an enlarger and have the same size photo as produced by a lens of twice the focal length. By doing, so I get the same size image, so arguments based solely on image size are negated, but the S/N and resolution will both deteriorate by a factor of 2, not 4, compared with using the longer lens.

Those are the physics and maths. Now, show me the maths and physics that says otherwise, not hand waving. But, I will write no more about this subject.